#include <bits/stdc++.h>
using namespace std;
vector <int> v[351];
int cap[351][351],cost[351][351],n,dist[351],s,d,S,D;
bool incoada[351];
int daddy[351];
priority_queue <pair<int,int>> pq;
pair <int,int> dijkstra()
{
    int i;
    for(i=1; i<=n; i++)
        dist[i]=1e9;
    dist[s]=0;
    pq.push({0,s});
    incoada[s]=1;
    int cst=0,flow=1e9;
    while(pq.size())
    {
        int x=pq.top().second;
        incoada[x]=0;
        pq.pop();
        for(auto it:v[x])
            if(cap[x][it]&&dist[it]>dist[x]+cost[x][it])
            {
                dist[it]=dist[x]+cost[x][it];
                daddy[it]=x;
                pq.push({-dist[it],it});
            }
    }
    for(i=d; i!=s; i=daddy[i])
        flow=min(flow,cap[daddy[i]][i]);
    for(i=d; i!=s; i=daddy[i])
    {
        cap[daddy[i]][i]-=flow;
        cap[i][daddy[i]]+=flow;
    }
    cst=flow*(dist[d]-S+D);
    return {flow,cst};
}
queue <int> q;
void bellman()
{
    for(int i=1; i<=n; i++)
        dist[i]=1e9;
    dist[s]=0;
    q.push(s);
    incoada[s]=1;
    while(q.size())
    {
        int x=q.front();
        incoada[x]=0;
        q.pop();
        for(auto it:v[x])
            if(cap[x][it]&&dist[it]>dist[x]+cost[x][it])
            {
                dist[it]=dist[x]+cost[x][it];
                if(!incoada[it])
                {
                    incoada[it]=1;
                    q.push(it);
                }
            }
    }
}
int main()
{
    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);
    int m,i,a,b,c,k,j;
    cin>>n>>m>>s>>d;
    for(i=1; i<=m; i++)
    {
        cin>>a>>b>>c>>k;
        cost[a][b]=k;
        cost[b][a]=-k;
        cap[a][b]=c;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    bellman();
    //for(i=1;i<=n;i++)
    //cout<<dist[i]<<" ";
    //cout<<'\n';
    S=dist[s];
    D=dist[d];
    for(i=1; i<=n; i++)
        for(j=1; j<=n; j++)
            cost[i][j]=cost[i][j]+dist[i]-dist[j];
    pair <int,int> x;
    int cost=0,flow=0;
    do
    {
        x=dijkstra();
        flow+=x.first;
        cost+=x.second;
    }
    while(x!= make_pair(0,0));
    cout<<cost;
    return 0;
}